Method of removing copper oxide from copper



Jan. 8, 1929.

H. s. LUKENS ET A1.

METHOD OF REMOVING COPPER OXIDE FROM COPPER Filed March 5l. 1924. 2 Sheets-Sheet 1 GAS ma To ankam: mcmonn CARBON ELCTROE .4.'oPnOnAL ALPOLE PLAT E 5C RUBBER 0R PREUFITATOK lTILTIN HECMNHSN IMPURE COPPER MELTINGa FURNMZE SLA@ +Mw/figo M ELTING FURNMIE 0 w w L f W m3 m M we mmm s ww fam Mw M Tm mms. WE MEO Am ww um a. mn mm wm `R Mw mw xm 0 6 O m 0: 5 60 MX E T W N IIIW' G R mm E man. a mmm V|..|.||.v. Mam

INVENTUM. l? il fir/afm Jan. 1929 1 1,698,443

`H. S. LUKENS ET AL METHOD OF REMOVING COPPER OXIDE FROM COPPER Filed March 5l. 1924 2 Sheer,s--Shee1I 2 50MB @UPPER AND SLA@ SOLID COPPER AND MQW D WITNESS: INV EN TORS. l

CII

Patented Jan. 8, 1929.

tlNlTED S'lA-lES" HIRAM S.

LU'KENS AND RUSSELL P. HEUER, OF IPHLADELPHIA, PENNSYLVANIA.

METHOD 0F REMOVING COPPER OXDE FROM COPPER.

Application filed March 31, 1924.

Our invention relates to the deoxidation ot copper.

@ur main purpose is to deoxidize molten copper by and to use the slag over and over, reducing the oxide taken up by the slag either between the deoxidizing uses ot the slag or preferably when circumstances permit continuously during` the deoxidizing use oi the slag.

It further purpose is to continuously deoxidize the slag during` its use, either chemically or electrolytically, so as to maintain its effectiveness. i

A. further purpose is to pass molten copper intermittently or continuously-through a bath in which its copper oxide is with drawn by a slag.

A further purpose is to provide a slag above the molten metal and immiscible to the metal, into which the copper oxide Within. the metal may di''luse and in which the diffused copper oxide may be reduced chemically or electrically or otherwise to permit. continued. diffusion and extraction ot' the copper oxide from the metal into the slag. y

ri further purpose, alternatively is to provide for intermittent or progressive removal. of portions ot the slag; tor treatment to reduce its copper oxide content with corresponding substitution o' fresh slag low in copper oxide for that removed.

A 'further purpose 1s to contnniously take out copper oxide from a slag` surinoimtinp` a bath ot .molten copper by electroyltic action.

A li'lrther purpose is to utilize a dcoxidif/.ingl slag` tor deoxidizingg a bath ot molten metal :it the same time that it is being treated by a reducing` means, chemical or electrolytic, to prevent accumulation of oxide in the slap; and to return to the bath the tree metal ot the oxide removed, pret'- crably making` the molten metal one ot' the electrolytic poles when the clectrolytic method used.

Further purposes will appear in thespeci iication and inthe claims.

Our invention relates both to the metl'iods or processes involved and to apparatus by which these methods or processes may be carried out.

Figure l is a vertical section of diagrammatic apparatus using' our invention.

Figures 2 and 3 show diagrammatically desirable arrangements of or schemes for operation, somewhat dierent in the two Serial No. 703,122.

igures to accommodate difference in the raw material requiring purification.

Figure l is a ternary diagram 'for the ternary system of copper, copper-oxide and a hypothetical slag, showing the tie,lines at one temperature.

Figures 5, 6, 7 and 8 are each representative of (litter-ent experimental testsV or series oi" tests, showing the experimentally deter` mined tie-lines el' the two liquid phases with different slags. n

Commercial copi erhas been subject to the disadvantage ot containing` a small percentage of copper oxide in spite ot many efforts otl di'tl'erent kinds to remove the copper oxide. This percentage in the best copper available has approximated 1/2 ot 1%. 'llhough small in quantity, this oxide has seriously affected the copper in altering its physical properties and, more particularly, in increasing` its electric resistance.

Efforts have been made to improve the copper by laboratory use ot slags to remove the oxide ot copper from the copper, but this has never been capable et extensive use because of its laboratory cl'iaracter and prt marily because the sla-,93s have never been treed from the absorbed copper oxide, the copper has not been improved greatly and the operation has never been made a continuous one.

llectrolytic copper might at first glance seem to avoid this objection by being` wholly tree from copper oxide. However, it is not possible to use the electrolytic copper in the form deposited without.recastinp. .ln this recrstinggl process, copper oxide terms and dissolvesI within the molten. copper. To correct this., carbon, hydrocarbons, etc.. have been introduced .vithin and upon the molten copper, whereby the oxide content is reduced to about 1/2 ot 1% copper oxide. This amount however' remains in commen cial copper and its ill-effect has been well recognized. Elliorts have been made to further remove it by carbon, hydro-carbons, etc., but if the reduction be continued the copper liberates a whilst cooling in the molds and the castings are unsuited for use. These gases seem to gain access to the copper with the direct contact ot copper and oxide reducing` agents.

By our invention we deoxidize molten copper by floating` upon its surface a suitable slag. Deox'idation results from the transfer ot copper oxide to Vthis slag. The

mechanism of such transfer is evident from consideration ottlre phase rule relations governing the distribution ot' one component, copper oxide between two liquid phases, a, slag-rich phase and a copper-rich phase.

When molten copper containing copper oxide comes into contact with an oxide-tree slag the partial free energy of copper oxide in the copper is contrasted with the zero partial free energy oi copper oxide in the slag. Copper oxide moves into the slag from the copper to an extent determined by its partial tree energies in the copper and in the slag, respectively, flow of copper oxioe from the copper into the slag ceasing when the rising partial troc energy of copper oxide in the slag and the falling partial fre-c en ergy of copper oxide in the copper reach the same level. At the same level of partial free energ, different slags may have very different concentrations of copper oxide, which accounts for their corresponding diiferent etl'ectivenesses for the removal of copper oxide from the molten copper. lhatever the slag there will at equilibrium be a definite concentration of copper-oxide in the slag for each concentration (no matter how small) in the copper, so that any one or many different slags may be used, but with very different eifectivenesses. le suggest a number which we have tried but without any thought that the list is complete nor that ity includes all of the more highly eilcctive slags In the slag deoxidation, to remove copper oxide so thatV the slag may be used again or may be used continuously, the slag is treated to remove copper-oxide.Y By electrolysis or other means the concentration of copperoxide in the slag may be reduced practically to Zero, and it follows that the copper phase in equilibrium with such slag will approximate Zero content of copper-oxide.

Ve remove the copper-oxide from the molten copper by bringing the latter into contact with a slag and treat this slag to keep its copper-oxide content at or below a required amount.

While any slag which is effectively immiscible with molten copper and mi'scible with molten copper-oxide will serve the purpose, not all operative slags work equally well. Properties, melting-point, viscosity, vapor pressure, stabilityetc., will favor certain slags. Other factors that may deter` mine or aiect the choice of a slag will be local conditions, rapidity and effectiveness. in functioning and laclt of corrosiveness to furnace linings.

The equilibrium distribution of copperoXide within the copper and within the slag will be better understood byr a brief discussion of this subject from the standpoint oi binary and ternary component relations between the molt-en two component system,

copper-oxide and copper, and the molten three component system copper-oxide, copper and slag, as follows Our slag deoxidation put-s to useful application these phenomena which occur when a molten, two-component system* copper and copper-oxitle-is brought into contact with a third component-a slag, iinmiscible with molten copper and miscible with molten copper-oxide. The construetion ot a ternary diagramCu, C1120, slag-will show the resultant equilibria.

For a. perfectly general treatment, we assume-any slag, and develop the two binary equilibrium diagrams- Cu plus slag and Cu2() plus slag-tor temperatures exceeding the liquidus curves. To these can be added the binary diagram, Cu plus CugO, as determined by Slade and Farrow, (Proc. Roy. Socy, 1912, LXXXVII, page 52a).

Since copper shows such limited liquid miscibility with both slag and oxide, most concentrations on the ternary diagram will show two liquids in equilibriumwone, in general, rich in slag, the other rich in copn per; the total Cu2() present being divided between these two liquid phases. (See diagram, Figure Lt.)

The composition of the liquid phase or phases presentin the three-component system, copper, copper-oxide and slag, at. a given temperature is graphically indicatedv in the ternary equilibrium diagram of Figure 4, which shows a diagram with a hy-v pothetical slag miscible when molten with molten copper-oxide and immiscible with molten copper.

This diagram shows that within the area abcd two immiscible liquids coexist for every ratio otI the three components of the system. The composition of the one liquid (being molten slag containing dissolved copper oxide and some copper) will vary along de with the simultaneous variation ot the conjugate liquid (molten copper containingl dissolved copper-oxide and, theoretically, some slag) along ab. For any given composition on a?) (showing the copper-oxide content oi the copper), only one coi'nposition on col (showing the copper-oxide content oi the slag) can be maintained in equilibrium. The tie lines, such as fg, 71.7', etc., illustrate this relationship; compositions f and It ot the impure copper require compositions gf and j respectively of the impure slag.

le have experimentally determined the compositions of the co-existing liquids (impure copper and impure sla-g) for the lower portion 'of the ternary diagram for quite a number of different slags, with results that are plotted in Figures 5, 6, 'Z and 8 with an assumption (substantially true) of negligible solution of slag into the copper and of negligible solution of copper into the slag.

lill

lill

Lacey-iis These tie-lines are self-enplanatory, the composition of the slag used being; noted upon each tie-line. Freni these figures it will be noted that. there is a Wide divergence in the etiectivenesses ot the slags used. Among the better slags are seen to be the chlorides oi? calcium or bariuin niixed with a, litt-le sodium berate, and the chlorides of sodiuni or potassium mixed with a little sodium silicate, phosphate or berate. Sodium silicate alone and the chloride of i'iotassiuni or sodium alone is seen to be less ell'ective.

Figure l, illustrates one et niany arrangements if'or carrying` out, our process. Molten copper is intrmluced at into the body 16 ot the deo. idr/ling` tui-nace 1T. i trunnion and tilting;` ineclianieni is indicated diagraminatically tor periodic pouring after the cog-- pf-r has been deoxiiilined or desired the discliarge niay be by oi'eriloiv (intermittent or continuous) at a spout lll. Vllhe retractory 19 seals tbe slap; lroni ille copper inlet and outlet and keeps ille heat in the furnace. Abm/'o the slap' which covers the niolten copper may be aovnntagwuslv Vfloated a layer ot carbon to help deoiidize the slag, or (and) a reducing p jas or hydrocarbon inigjglit be. :introduced ,into tbe slag or above th sl" e; as at Qt), 20 respectively, 'for the saine purpose. liberated carbon monoxide or other gas el'l'luent escapes trein the furnace at 2l. Positive electrodes fil and 25 are provided above the slag 'for electrolytic deposit-ion ot the copper of the Cu2@ dill'used from the metal. bath into the The niolten copper of the bath toi-ins the negative electrode, electric connection being made :troni it, as indicated diagrammatically at 2G, to the source ot direct current, not shown.

lloruiall57 the electric resistance of the slag and carbon above the slap; will be considerably less than the resistance oit the slag proper, with the resi 't that the slag-carbon mixture above the slap," acts as a continuous positive electrode covering; the whole ,flag balli. The ele tl rolytic deposition oii me copper is upon the copper ol: the bath. it will be obvious that -the oxide ot the slap; ie continuously reduced by both the electji'olytic action of the current and by the carbon lloating upon the slag; and that it desired either may be used without the other.

lt it be desired to supply Yadditional heat to this reducing tiunace, an alternating voltage may be impressed across the two carbon electrodes shown or across any other suitable electrodes (such as the pole pieces shown), the and nietal bath being,` thereby used as a resistor tor heating purposes Figure 2 indicates an advantageous scheine tor carrying out our process when the raw material requiring purification is substantially 'free troni other metals or niet-allie oxides than et copper. The raw material is clnirged in toe melting furnace, and the inolten product containing` copper oxide as inpuriiv delivered continuously or internntleiitly to the deoxidizing.furnace which nia)r advaiitageously be as shown in `Figure l.

lt is quite deffii'uble to perform the inelting;` suliic distance troni Jdie deoxidiaiup] iurnace or container or under such conditions as to :tree the latter 'trein -the deteriorating` etlect upon the slag ci the gases attending,l fuel combustion, so as to perniit selection oit slugs independently ot this tactor and thus permit the use of cheapA fuel heating.

` 'ie rav.' material contain metallic iinpurities, these impurities may be removed. in this process. Figure 3 .illustrates a scheine ot operation which accomplishes this. The slowing tiunace shown receives niolten ine ,ai with impurities, ironi the melting iurnace. lt this nietal be oxidized, oxides of the metallic inipuritiessuch as Pb@ accompany the copper oxide into the slag'. lt is to be noted, however, that the iuetals noble than con e" it be lir \l let ci iper uns c onu .Aci ocioie any copper oxide will be present because the copper oxide would otherwise be decomposed to il' Vin the oxides of these other metals. 'illus ordinarilj,7 becoines oi' little importance here because the other inetals vie ved as inn puriiies are small in total quantity.

The impure'slag1 is Withdrawn continuously or intermittently and reduced in the separate reducing furnace to avoid containinating the dcoxidized inetal With the reduction products of the slag. lllfith strong' reducinggv agents there may be slight disadvantageous reduction of a portion oi the original slag. This is advantageously corrected by treating' the reduction product :l'roin the reducing furnace with a suitable sinall portion of the unreduced slag' Wnicli reoxidixes the reduced portion ot the slag for eturn with the slap; product troni the reducing' furnace to the slugging' 'furnace as indicated.

bviously there may be a very Wide variation in the details of our process4 accordinv to the Whiin or particular neel ot the user and We claiin all such in so tai' as they fall Within the reasonable spirit and scope of our invention.

lla-ving thus described our invention, what we claini as new and desire to secure by Let ters Patent is l. rllhe process of freeing' molten copper from the copper oxide dissolved in it, which consists in providing a medium into which the oxide will '(li'lliise, taking up the oxide in the niediuin, removing; the oxide trein the absorbing i iediuin and repeating the operation.

2. The process ot freeing molten copper 'from the copper oxide dissolved in it, to purify the copper, Which consists in reinovlll' lill:

ing lthe oxide from the copper at the surface of the molten copper and returning the metal of the oxide to the surface of the copper while keeping lthe copper free from combination with the agent used in the removal.

3. The process of freeing molten copper from the copper oxide dissolved in it, to purify the copper, which consists in removing the oxide from the copper at the surface of the molten copper and concurrently returning the metal of the oxide to the surface of the copper While keeping the copper free from coinbination with the agent used in the removal.

e. In the art of removing copper oxide from molten copper by means of a slag, the invention which consists in slagging preliminarily melted copper With a material in which copper-oxide has low partial free energy as compared to its partial free energy in the same concentration in the mole ten copper, and Vtreating the slag' for use again.

5. In the art of removing copper oxide from molten copper by means of a slag, the step which consists in slagging the molten copper with a slag having lower partial free energy of copper oxide than the partial free energy of the copper oxide in the copper, and treating the slag for use again.

6. The process of deoxidizing molten copper While keeping it free from added impurity which consists in covering the molten copper With slag capable of taking up copper f oxide from the copper, taking up the copper oxide and treating the slag in place to reduce its copper oxide Without adding any of the initial to the copper.

7. The process of treat-ing molten copper to remove its copper oxide While keeping it free from added impurity which consists in treating the surface of the copper with slag, taking up the copper oxide While progressively deoxidizing the copper oxide in the slag and Without adding any of the initial slag to the copper.

8. The process of deoxidizing molten cop per continuously While keeping it free from added impurity, Which consists in covering the molten copper with slag capable of taking up copper oxide from t-he copper and treating the slag in place as a continuing operation to reduce its copper oxide, the reduction of the copper oxide going on in the slag While the copper oxide is beingl extracted by the slag from the copper and without adding)` any of the initial slag to the copper.

9. The process of cleoxidizing molten copper continuously While keeping it free from added impurity7 which consists in covering the molten copper with slag capable of taking up copper oxide from the copper, taking up the copper oxide and reducing the copper oxide in the slagV in position by a chemical reducing agent to maintain the effectiveness of the slag and Without adding any of the initial slag to the copper.

10. The process of deoxidizing molten copper continuously keeping it free from added impurity which consists in covering the molten copper with slag capable of taking up copper oxide and chemically removing copper from the copper oxide content of the slag, as a continuing operation While it taking up copper oxide from the copper and Withoutl adding any ofthe initial slag to the copper.

ll. The process of deoxidizing molten copper continuously, which consists in covering the molten copper with slag capable oit taking np copifer oxide from the copper and elcctrolytically removing copper from the copper oxide the slag and depositing it on tlc molten surface of the c pper.

l2. The process of deoxidizing molten cop- -ier continuously which consists in covering the molten copper with slag capable of taking up copper oxide and electrolytically removinf` copper from the copper oxide content or the slag, as a continuing operation While it is taking up copper oxide from the copper.

13. The process of deoxidizing copper by a slag having relatively high partial free energy as compared to the partial free energy of copper oxide in the same concentration in other slags at the same temperature, which consists in removing copper oxide from the slag While the slag` is being used to slag the copper and thus keeping the copper oxide in the slag quantitatively so low as to permit continued diffusion of copper oxide from the copper into the slag.

lil. The process of freeing molten copperI from the copper oxide dissolved in it, which consists in lproviding a pool of molten copper, supplying()l molten copper with dissolved copper oxide in it to the pool at one point and withdrawing molten copper from the pool at another point While removing the oxide from the metal of the pool by diffusing the oxide into a slag and maintaining the absorbing capacity of the slag.

l5. The process of freeing molten copper' from the copper oxide dissolved-in it, Which consists in melting copper at one point, transferring it molten to another point Where it is free from the conditions surrounding' the melting and removing the oxide from the copper in the second position by diffusion into a slag which would be deteriorated by the gases attending fuel coinbust-ion.

16. The process of freeing molten copper from the copper oxide dissolved in it, which consists in melting copper at one point, transferring it molten to another point Where it is free from the conditions surrounding the melting, removing the oxide from the Sli Cil

Coppel.' in the Second position by dilfusion into u slag which. would be deteriorated by 'the gases attending Yliiel combustion and i'emoving the molten purified coppe?.

17. The process, of freeing molten copper 'from the copper oxide diSSoli/ed in it, which consists in melting` copper :it one point, tiaileiei'i'ing it molten to :mother point Where it is l'i'eo from the conditionsI surrounding the nieltiug7 ie Hoving the oxide from the Copper 10 in the second position by diffusion into zi slag which would be deteriorated by the attending fuel combustion and reducing the @opper oxide in the slag' so as to pei'- init use of the same slag over and over again.

HRAM S. LUKENM RUSSELL P. HEUER. 

